Mechanistic Study of Photoelectrochemical Reactions at a p-GaP Electrode

概要

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The photocurrent-potential relations of a p-GaP electrode in various solutions are studied potentiostatically. Both the cathodic and anodic photocurrents are observed, i.e., the sign of photocurrent changes at a certain potential which we name the potential of zero photocurrent, Vzp. The potential of zero photocurrent is close but not equal to the flatband potential. The origin of the anodic photocurrent is presented. The log (photoeurrent)-potential relations follow the Tafel line at medium bias potentials and deviate from it at large and small bias potentials. The mechanism of the cathodic reactions is proposed based on the experimental results. The rate-determining step is the supply of photoexcited electrons to the semiconductor surface at large bias potentials and is the electrochemical, i.e., surface, process at medium and small bias potentials. At the small bias potentials, the photocurrent is enhanced by the photoelectrochemical reduction of oxidized species created by holes in valence band.
The Electrochemical Societyの論文